Packaging material and freshness pack

Abstract

The application discloses a packaging material, which comprises a main body layer and a heat-sealing layer arranged in sequence along the thickness direction, wherein the heat-sealing layer comprises a transition layer and a gas-permeable layer combined by multi-layer co-extrusion, the material of the transition layer comprises polyolefin, the transition layer has a porous structure, the material of the gas-permeable layer comprises a random copolymer with a plurality of polar ester group functional groups, a plurality of molecular chains in the random copolymer have diffusion channels therebetween, the diffusion channels are communicated with the porous structure, and the pore size of the porous structure is larger than that of the diffusion channels. The application further discloses a fresh-keeping bag.

Description

Technical Field

[0001] This invention relates to the technical field of flexible plastic packaging, specifically to a packaging material and a food preservation bag. Background Technology

[0002] Currently, the practice of adding preservatives to food packaging bags to extend the shelf life of food is gradually being abandoned by the public. The mainstream preservation technology is to preserve food by perforating paper-plastic composites or by using alcohol packaging materials made from exposed alcohol cards.

[0003] Alcohol-based packaging materials can affect the flavor of food.

[0004] Therefore, developing a packaging material and preservation bag that does not affect the flavor of food is an urgent problem to be solved in this field. Summary of the Invention

[0005] The present invention aims to address, to a certain extent, one of the technical problems in related technologies. To this end, the present invention provides a packaging material and a food preservation bag.

[0006] To achieve the above objectives, as a first aspect of the present invention, the present invention provides a packaging material comprising a main layer and a heat-sealing layer sequentially stacked along the thickness direction, the heat-sealing layer comprising a transition layer and a breathable layer bonded by multi-layer co-extrusion, the transition layer comprising a polyolefin having a porous structure, the breathable layer comprising a random copolymer having multiple polar ester functional groups, the random copolymer having diffusion channels between multiple molecular chains, the diffusion channels communicating with the porous structure, and the pore size of the porous structure being larger than the pore size of the diffusion channels.

[0007] Furthermore, the transition layer includes a transition layer body and a plurality of pore-forming particles dispersed in the transition layer body, wherein the material of the transition layer body is polyolefin.

[0008] Furthermore, the mass percentage of the pore-forming particles in the transition layer is between 20% and 80%.

[0009] Furthermore, the material of the transition layer body includes polypropylene and polyethylene, and the mass percentage of polypropylene in the transition layer body is not higher than 20%, while the mass percentage of polyethylene in the transition layer body is between 10% and 80%.

[0010] Furthermore, the material of the breathable layer includes a vinyl polar copolymer, and the ester functional groups include vinyl acetate and / or methyl acrylate.

[0011] Furthermore, the material of the breathable layer includes ethylene-vinyl acetate copolymer and ethylene-methyl acrylate copolymer, and the ratio of ethylene-vinyl acetate copolymer to ethylene-methyl acrylate copolymer in the breathable layer is between 0.5 and 2.5.

[0012] Furthermore, the transition layer is disposed on the side of the heat-sealing layer close to the main body layer, the breathable layer is disposed on the side of the heat-sealing layer away from the main body layer, the outer surface of the transition layer is in contact with the inner surface of the main body layer, and the inner surface of the transition layer is in contact with the outer surface of the breathable layer.

[0013] Furthermore, the main body layer includes a printing layer and a support layer stacked sequentially along the thickness direction. The material of the printing layer includes matte polypropylene, and the material of the support layer includes polyethylene nonwoven fabric. The printing layer and the support layer are adhesively bonded together, and the polyethylene nonwoven fabric is adhesively bonded together with the heat-sealing layer.

[0014] Furthermore, the heat-sealing layer comprises nine co-extruded functional films. The composition and content of the first functional film satisfy the following: 10% to 30% linear low-density polyethylene, 0% to 30% metallocene polyethylene, and 40% to 70% calcium powder. The second to sixth layers have the same composition and satisfy the following: 50% to 80% linear low-density polyethylene, 0% to 20% polypropylene, and 40% to 70% calcium powder. The seventh, eighth, and ninth layers have the same composition and include vinyl acetate and / or methyl acrylate.

[0015] As a second aspect of this application, this application provides a food preservation package, which includes a preservative and a packaging bag. The packaging bag is made of the aforementioned packaging material. The packaging bag includes a heat-sealing layer and a main body layer stacked from the inside to the outside along the thickness direction. The heat-sealing layer is disposed on the inner side, and the main body layer is disposed on the outer side. A receiving cavity is formed between the heat-sealing layers, and the preservative is disposed in the receiving cavity.

[0016] By connecting the large-pore, porous structure of the transition layer with the small-pore molecular diffusion channels of the breathable layer, a multi-level gradient breathable channel is constructed. This allows the internal contents to achieve rapid evaporation for thorough sterilization while preventing liquid evaporation and overflow that could reduce food flavor. The large pore size reduces transmission resistance, while the small pore size controls the evaporation rate, ensuring rapid sterilization while preventing excessive contact between the preservatives and the food, which could lead to bitterness or flavor degradation. Secondly, the breathable layer uses a random copolymer containing polar ester functional groups. The interlaced molecular chains reduce crystallinity and create a loose space, giving the packaging excellent anti-contamination heat-sealing performance. Even when liquid preservatives are present at the heat-sealed edge, the sealing strength is maintained, effectively preventing leakage and improving production efficiency. In addition, the transition layer acts as a heat buffer to prevent the breathable layer from being burned by high temperatures. Combined with the soft main body layer, it ensures uniform stress during heat sealing, overcoming the shortcomings of traditional packaging materials that are stiff and brittle, and improving the mechanical stability and appearance of the packaging material.

[0017] These features and advantages of the present invention will be disclosed in detail in the following specific embodiments and accompanying drawings. The preferred embodiments or means of the present invention will be shown in detail in conjunction with the accompanying drawings, but are not intended to limit the technical solutions of the present invention. In addition, each of these features, elements and components appearing in the following text and drawings is a plurality of, and different symbols or numbers are used for convenience of representation, but all represent parts with the same or similar construction or function. Attached Figure Description

[0018] The present invention will be further described below with reference to the accompanying drawings: Figure 1 A schematic diagram of one embodiment of the packaging material provided by the present invention; Figure 2 A schematic diagram illustrating one embodiment of the food preservation bag provided by the present invention; Figure 3 This is a schematic flowchart illustrating one embodiment of the packaging material preparation method provided by the present invention.

[0019] Explanation of reference numerals in the attached figures 1: Packaging material; 10: Transition layer; 11: Breathable layer; 12: Main layer; 110: Diffusion channel; 101: Porous structure; 120: Printing layer; 121: Support layer; 2: Fresh-keeping bag; 20a: Front packaging layer; 20b: Back packaging layer; 21: Fresh-keeping agent; 201: Heat-sealing adhesive. Detailed Implementation

[0020] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described are intended to explain the present invention and should not be construed as limiting the invention.

[0021] The terms "an embodiment," "example," or "example" used in this specification refer to a particular feature, structure, or characteristic described in connection with the embodiment itself that may be included in at least one embodiment disclosed in this application. The phrase "in an embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment.

[0022] It should be noted that in this invention, "inner side" refers to the side of the packaging bag that is close to the packaged item, and "outer side" refers to the side that is away from the packaged item.

[0023] The inventors of this application have discovered that adding preservatives to food to extend its shelf life is gradually being abandoned by the public. Traditional alcohol packaging materials, produced using perforated or exposed paper-plastic composites, lack a slow-release effect and negatively impact the food's flavor; furthermore, direct contact between the food and the evaporating surface can cause the food to taste bitter. For non-perforated packaging, the alcohol evaporation rate is too slow to achieve sterilization. Additionally, unavoidable spillage during the bottling process significantly reduces production efficiency. Therefore, developing an alcohol packaging material that simultaneously provides slow release, sterilization, high production efficiency, contamination resistance, and single-sided evaporation is of great significance for people's pursuit of a high-quality life.

[0024] To achieve the above objectives, as a first aspect of the present invention, the present invention provides a packaging material, such as... Figure 1 and Figure 2 As shown, the packaging material 1 includes a main body layer 12 and a heat-sealing layer stacked sequentially along the thickness direction. The heat-sealing layer includes a transition layer 10 and a breathable layer 11 bonded by multi-layer co-extrusion. The material of the transition layer 10 includes polyolefin and has a porous structure 101. The material of the breathable layer 11 includes a random copolymer having multiple polar ester functional groups. The multiple molecular chains in the random copolymer have diffusion channels 110 between them. The diffusion channels 110 are connected to the porous structure 101. The pore size of the porous structure 101 is larger than the pore size of the diffusion channels 110.

[0025] By connecting the large-pore porous structure 101 of the transition layer 10 with the small-pore molecular diffusion channels 110 of the breathable layer 11, a multi-level gradient breathable channel is constructed. This allows the internal contents to achieve rapid evaporation for thorough sterilization while preventing the contents from evaporating and overflowing in liquid form, thus reducing the food's flavor. The large pore size reduces transport resistance, while the small pore size controls the evaporation rate. This ensures rapid sterilization while preventing excessive contact between the preserved contents and the food, thus avoiding bitterness or other flavor issues. Secondly, the breathable layer uses a random copolymer containing polar ester functional groups. The interlacing of molecular chains reduces crystallinity and forms a loose space, giving the packaging material excellent anti-contamination heat-sealing performance. Even when there is liquid preservative contamination at the heat-sealed edge, it can still maintain the sealing strength, effectively preventing leakage and improving production efficiency. In addition, the transition layer acts as a heat buffer layer to prevent the breathable layer from being burned by high temperature. Together with the soft main body layer, it makes the heat sealing force uniform, overcoming the defects of traditional packaging materials that are stiff and brittle, and improving the mechanical stability and appearance of the packaging material.

[0026] Preferably, the porous structure of this application has pore sizes in the micrometer range, and the diffusion channels are molecular-level diffusion channels formed by the disruption of long molecular chains by polar ester functional groups. The difference in size between these channels creates a multi-level gradient of permeable transport channels. This multi-level diffusion channel allows liquid alcohol to be first polarly adsorbed and captured into small molecules by the polar ester functional groups. Without the flow restriction of molecular-level channels, alcohol would directly gush out in large quantities from the micrometer pores, causing an instantaneous excessively high alcohol concentration on the food surface and resulting in a bitter taste. The gradient channel achieves a "slow first, fast later" effect, ensuring sufficient total volume while avoiding localized overconcentration. The flow restriction effect of the molecular-level channels makes alcohol release more prolonged, extending shelf life. On the other hand, this gradient structure also effectively optimizes the temperature transfer of heat from the outside to the inside during heat sealing, significantly reducing the heat-sealing temperature when it reaches the permeable layer. This prevents over-melting and film breakage, allowing the permeable layer to fully melt at a suitable temperature and fuse with the permeable layer of another packaging material to form a uniform seal, avoiding leakage points caused by localized overheating or underheating.

[0027] This application does not impose special limitations on the porous structure of the transition layer, as long as it meets the requirement of a porous structure. The form of formation is not limited; for example, a porous structure can be formed by adding air bubbles, foaming agents, or pore-forming agents. Preferably, the transition layer includes a main body and multiple pore-forming particles dispersed within it. The main body is made of polyolefin, and the pore-forming particles are incompatible with the polyolefin material. When dispersed within the polyolefin, the incompatible interfaces easily separate to create pores, forming a porous structure. These pore-forming particles provide a more uniform distribution of pores. Furthermore, the embedding of these particles within the polyolefin can regulate heat transfer during heat sealing, reducing the heat reaching the permeable layer. Preferably, the pore-forming particles include calcium powder, which effectively breaks down the molecular chains of the polyolefin film and forms fine micropores at the interface. Calcium powder itself has adsorption properties, enabling it to adsorb alcohol and increase the evaporation rate. Preferably, the mass percentage of the pore-forming particles in the transition layer is between 20% and 80%, meaning that the porosity of the porous structure is between 20% and 65%.

[0028] This application does not impose any special restrictions on the specific composition of polyolefin in the transition layer, as long as it meets the requirement of polyolefin. Preferably, the main material of the transition layer includes polypropylene and polyethylene, and the mass ratio of polypropylene in the main body of the transition layer is not higher than 20%, while the mass ratio of polyethylene in the main body of the transition layer is between 10% and 80%. Polypropylene has better thermal insulation properties than polyethylene, and adding an appropriate amount can improve the thermal insulation effect of the transition layer.

[0029] This application does not impose specific limitations on the material of the breathable layer, only requiring that it be a random copolymer with polar ester functional groups. Preferably, the material of the breathable layer includes a vinyl polar copolymer, and the ester functional groups include vinyl acetate and / or methyl acrylate. EVA (ethylene-vinyl acetate copolymer) is polymerized from two monomers, ethylene and vinyl alcohol (VA), while EMA (ethylene-methyl acrylate copolymer) is polymerized from two monomers, ethylene and methyl acrylate (MA). Compared to the single molecular chain of polyethylene, the introduction of MA and VA into the molecule disrupts the original order of the molecular chain, significantly reducing the overall crystallinity. This adds many loose spatial structures to the originally tightly packed molecules, allowing smaller molecules such as water vapor and gaseous alcohol to pass through. In other words, the higher the proportion of MA and VA composite, the lower the crystallinity and the less resistance to alcohol passage. Furthermore, mixing ethylene chains with different MA and VA contents, with different molecular chains intersecting, can further reduce molecular crystallinity and increase the channels for alcohol molecules. When misalignment occurs during the production process, the alcohol transforms from liquid to gaseous during the heat-pressing process. This gaseous vapor evaporates rapidly through the loose spatial structure, achieving an anti-contamination effect without affecting the seal strength. This enables stable and rapid production of alcohol packaging materials.

[0030] Preferably, the breathable layer is made of ethylene-vinyl acetate copolymer and ethylene-methyl acrylate copolymer, with the ratio of ethylene-vinyl acetate copolymer to ethylene-methyl acrylate copolymer in the breathable layer being between 0.5 and 2.5. Using a mixture of these two materials improves production stability. During the machine operation, the mixture provides materials with multiple melting points, widening the heat-sealing melting temperature range, increasing the temperature resistance zone of the breathable layer, reducing the risk of burns and leaks. When heat-sealing alcohol packaging, staggered alcohol droplets may fall onto the edge of the heat-sealing layer; the breathable membrane composed of the mixture can resist foreign contamination and improve heat-sealing performance.

[0031] As an alternative implementation, the transition layer 10 is disposed on the side of the heat-sealing layer close to the main body layer 12, and the breathable layer 11 is disposed on the side of the heat-sealing layer away from the main body layer 12. The outer surface of the transition layer 10 is bonded to the inner surface of the main body layer 12, and the inner surface of the transition layer 10 is bonded to the outer surface of the breathable layer 11.

[0032] In some embodiments, such as Figure 1 As shown, the main body layer includes a printing layer 120 and a support layer 121 stacked sequentially along the thickness direction. The material of the printing layer 120 includes matte polypropylene, and the material of the support layer 121 includes polyethylene nonwoven fabric. The printing layer 120 and the support layer 121 are bonded together with adhesive, and the polyethylene nonwoven fabric is bonded together with the heat-sealing layer.

[0033] The heat-sealing layer comprises nine co-extruded functional films. The composition and content of the first functional film meet the following requirements: 10% to 30% linear low-density polyethylene, 0% to 30% metallocene polyethylene, and 40% to 70% calcium powder. The second to sixth layers have the same composition and meet the following requirements: 50% to 80% linear low-density polyethylene, 0% to 20% polypropylene, and 40% to 70% calcium powder. The seventh, eighth, and ninth layers have the same composition and include vinyl acetate and / or methyl acrylate.

[0034] This application does not impose special limitations on the thickness of the transition layer and the breathable layer, as long as they are multi-layered co-extruded. Preferably, the thickness of the transition layer is greater than that of the breathable layer, which can create an effective heat buffer. During heat sealing, heat is transferred from the external heat sealing blade to the inside. With a thicker transition layer, the heat transfer path from the outside to the inside is longer. Combined with the heat absorption of the polyolefin component, the temperature reaching the breathable layer is significantly reduced. The thicker transition layer ensures that the breathable layer is in a mild temperature range during heat sealing, which is sufficient to melt without overheating, avoiding problems such as burns and leakage. Secondly, the transition layer provides the necessary strength to make the packaging material move stably on high-speed packaging machines, and the film is not easily torn during bag making, filling, and transportation.

[0035] As a second aspect of this application, this application provides a food preservation bag 2, such as Figure 2As shown, the preservation bag 2 includes a preservative 21 and a packaging bag. The packaging bag is made of the above-mentioned packaging material. The packaging bag includes a heat-sealing layer and a main body layer 12 stacked from the inside to the outside along the thickness direction. The heat-sealing layer is located on the inner side, and the main body layer 12 is located on the outer side. There is a receiving cavity between the heat-sealing layers, and the preservative 21 is located in the receiving cavity.

[0036] In some embodiments, the packaging bag includes a front packaging layer 20a and a back packaging layer 20b. The front packaging layer 20a includes a perforated matte polypropylene layer, a front polyethylene nonwoven fabric, and a front heat-sealing layer arranged from the outside to the inside along the thickness direction. The back packaging layer 20b includes a matte polypropylene layer, a back polyethylene nonwoven fabric, and a back heat-sealing layer arranged from the outside to the inside along the thickness direction. The perforated matte polypropylene layer and the front polyethylene nonwoven fabric are bonded together with an adhesive, and the front polyethylene nonwoven fabric and the front heat-sealing layer are bonded together with an adhesive. The front heat-sealing layer and the back heat-sealing layer are connected by a heat-sealing adhesive 201. Specifically, the polyethylene nonwoven fabric has an oil resistance rating of 3-8 and a basis weight of 25 g / m2 to 50 g / m2. The napped side of the polyethylene nonwoven fabric is bonded to the corona-treated side of the heat-sealing layer.

[0037] Preferably, the perforated matte polypropylene has a corona-electrode surface for printing patterns, with an overall thickness of 12µm. The perforated matte polypropylene is composite with a glossy surface of polyethylene nonwoven fabric. The needle type used in the perforated matte polypropylene includes at least one perforation size among 1*1, 1.5*1.5, 2*2, 3*3, 4*4, 5*5, 6*6, and 7*7.

[0038] In some embodiments, after laminating with solvent-free adhesive, the packaging material is cured at 30-45°C for 24 to 30 hours to obtain a food preservation package.

[0039] In one specific embodiment, the method for preparing the food preservation bag is as follows: Figure 3 As shown, it includes: The heat-sealing layer is prepared by nine-layer co-extrusion, wherein the components of the first to sixth layers include polyethylene, polypropylene and calcium powder, and the components of the seventh to ninth layers include ethylene-vinyl acetate copolymer and / or ethylene-methyl acrylate copolymer. The printing layer and the support layer are bonded together with solvent-free polyurethane adhesive to obtain the main body layer; The main layer and the heat-sealing layer are bonded together with solvent-free polyurethane adhesive to obtain the intermediate product of the packaging bag; Two intermediate products in two packaging bags are heat-sealed together to obtain a fresh-keeping bag. The intermediate products in two packaging bags are stacked, with the two heat-sealed layers facing each other and a preservative placed between the two heat-sealed layers. The intermediate products in two packaging bags are then heat-sealed together using a heat-sealing adhesive.

[0040] The present invention will be further described below with reference to the embodiments.

[0041] Example Example 1 This embodiment provides a food preservation package, which includes a preservative and a packaging bag. The packaging bag includes a heat-sealing layer and a main body layer stacked from the inside to the outside along the thickness direction. The heat-sealing layer is located on the inner side, and the main body layer is located on the outer side. A receiving cavity is formed between the heat-sealing layers, and the preservative is placed in the receiving cavity. The main body layer includes a printing layer and a support layer stacked from the outside to the inside. The printing layer is composed of matte polypropylene with perforations on the front and matte polypropylene without perforations on the back. The support layer is made of polyethylene nonwoven fabric. The printing layer and the support layer on the front and back of the packaging bag are laminated with solvent-free polyurethane adhesive to obtain the main body layer. The main body layer is then laminated with the heat-sealing layer using solvent-free adhesive. The thickness of the matte polypropylene in the printing layer is 18 μm, the perforation size of the matte polypropylene on the front is 1*1 mm, the basis weight of the polyethylene nonwoven fabric in the support layer is 40 g / m², and the thickness of the heat-sealing layer is 30 μm. The specific components and proportions of the heat-sealing layer are as follows: First layer: 15% linear low-density polyethylene + 25% metallocene polyethylene + 60% calcium powder; Second layer: 55% linear low-density polyethylene + 45% calcium powder; Third layer: 55% linear low-density polyethylene + 45% calcium powder; Fourth layer: 55% linear low-density polyethylene + 45% calcium powder; Fifth layer: 55% linear low-density polyethylene + 45% calcium powder; Sixth layer: 55% linear low-density polyethylene + 45% calcium powder; Seventh layer: 100% EVA; Eighth layer: 100% EVA; Ninth layer: 100% EVA. The first to ninth layers are arranged from the outside to the inside, and the first to ninth layers are bonded together by nine-layer co-extrusion.

[0042] Example 2 This embodiment provides a food preservation bag structure identical to that of Embodiment 1, except that the specific components and proportions of the heat-sealing layer are different. The specific components and proportions of the heat-sealing layer satisfy the following: First layer: 25% linear low-density polyethylene + 15% metallocene polyethylene + 60% calcium powder; Second layer: 45% linear low-density polyethylene + 35% calcium powder + 10% polypropylene; Third layer: 45% linear low-density polyethylene + 35% calcium powder + 10% polypropylene; Fourth layer: 45% linear low-density polyethylene + 35% calcium powder + 10% polypropylene; Fifth layer: 45% linear low-density polyethylene + 35% calcium powder + 10% polypropylene; Sixth layer: 45% linear low-density polyethylene + 35% calcium powder + 10% polypropylene; Seventh layer: 100% EMA; Eighth layer: 100% EMA; Ninth layer: 100% EMA.

[0043] Example 3 This embodiment provides a food preservation bag structure identical to that of Embodiment 1, except that the specific components and proportions of the heat-sealing layer are different. The specific components and proportions of the heat-sealing layer satisfy the following: First layer: 25% linear low-density polyethylene + 15% metallocene polyethylene + 60% calcium powder; Second layer: 45% linear low-density polyethylene + 35% calcium powder + 10% polypropylene; Third layer: 45% linear low-density polyethylene + 35% calcium powder + 10% polypropylene; Fourth layer: 45% linear low-density polyethylene + 35% calcium powder + 10% polypropylene; Fifth layer: 45% linear low-density polyethylene + 35% calcium powder + 10% polypropylene; Sixth layer: 45% linear low-density polyethylene + 35% calcium powder + 10% polypropylene; Seventh layer: 70% EVA + 30% EMA; Eighth layer: 70% EVA + 30% EMA; Ninth layer: 70% EVA + 30% EMA.

[0044] Comparative Example Comparative Example 1 This comparative example provides a commercially available food preservation bag composed of PET and PE.

[0045] Test case Performance tests were conducted on Examples 1 to 3 and the comparative examples, and the results are shown in Table 1.

[0046] Table 1 Performance test results of the examples and comparative examples

[0047] As shown in Table 1, the embodiments of this application can be heat-sealed at a lower initial sealing temperature, indicating that the transition layer has good thermal insulation performance for heat-sealing temperature, and the material of the heat-sealing layer can achieve heat-sealing adhesion at a lower temperature. At the same time, the synergistic transport of the diffusion channels and porous structure of this application allows the internal alcohol to evaporate and dissipate in a gaseous form more quickly, which can not only fully sterilize but also prevent alcohol from seeping out in liquid form and contaminating the food flavor. In addition, for heat-sealing packaging bags when packaging alcohol, the heat-sealing structure of this application has multiple polar ester functional groups, which break long molecular chains, allowing the alcohol on the heat-sealed edge to be quickly absorbed and evaporated during heat sealing, resisting alcohol contamination and improving the heat-sealing bond strength.

[0048] The preservation packages of Examples 1 to 3 were subjected to standard tests, and the test results are shown in Table 2.

[0049] Table 2

[0050] As shown in Table 2, the food preservation bags made from the packaging materials of this application meet all the standards in terms of performance, and exhibit superior performance in terms of heat seal strength and alcohol evaporation rate, exceeding the performance of commercially available food preservation bags. Furthermore, the performance is even better when the internal breathable layer uses a mixed formulation.

[0051] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that the present invention includes, but is not limited to, the contents described in the accompanying drawings and the specific embodiments above. Any modifications that do not depart from the functional and structural principles of the present invention will be included within the scope of the claims.

Claims

1. A packaging material, said packaging material comprising a main layer and a heat-sealing layer sequentially stacked along the thickness direction, characterized in that, The packaging material is used for food preservation bags. The heat-sealing layer includes a transition layer and a breathable layer bonded by multi-layer co-extrusion. The transition layer is made of polyolefin and has a porous structure. The breathable layer is made of a random copolymer having multiple polar ester functional groups. The random copolymer has diffusion channels between multiple molecular chains, which are connected to the porous structure. The pore size of the porous structure is larger than that of the diffusion channels.

2. The packaging material according to claim 1, characterized in that, The transition layer includes a transition layer body and a plurality of pore-forming particles dispersed in the transition layer body, wherein the material of the transition layer body is polyolefin.

3. The packaging material according to claim 2, characterized in that, The mass percentage of the pore-forming particles in the transition layer is between 20% and 80%.

4. The packaging material according to claim 2, characterized in that, The material of the transition layer body includes polypropylene and polyethylene, and the mass percentage of polypropylene in the transition layer body is not higher than 20%, and the mass percentage of polyethylene in the transition layer body is between 10% and 80%.

5. The packaging material according to claim 1, characterized in that, The breathable layer is made of a vinyl polar copolymer, and the ester functional groups include vinyl acetate and / or methyl acrylate.

6. The packaging material according to claim 5, characterized in that, The breathable layer is made of ethylene-vinyl acetate copolymer and ethylene-methyl acrylate copolymer, and the ratio of ethylene-vinyl acetate copolymer to ethylene-methyl acrylate copolymer in the breathable layer is between 0.5 and 2.

5.

7. The packaging material according to any one of claims 1 to 6, characterized in that, The transition layer is disposed on the side of the heat-sealing layer close to the main layer, and the breathable layer is disposed on the side of the heat-sealing layer away from the main layer. The outer surface of the transition layer is attached to the inner surface of the main layer, and the inner surface of the transition layer is attached to the outer surface of the breathable layer.

8. The packaging material according to any one of claims 1 to 6, characterized in that, The main body layer includes a printing layer and a support layer stacked sequentially along the thickness direction. The printing layer is made of matte polypropylene, and the support layer is made of polyethylene nonwoven fabric. The printing layer and the support layer are bonded together with adhesive, and the polyethylene nonwoven fabric is bonded together with the heat-sealing layer with adhesive.

9. The packaging material according to any one of claims 1 to 6, characterized in that, The heat-sealing layer comprises nine co-extruded functional films, wherein the composition and content of the first functional film are: 10% to 30% linear low-density polyethylene, 0% to 30% metallocene polyethylene and 40% to 70% calcium powder. The second to sixth layers have the same composition and meet the following requirements: 50% to 80% linear low-density polyethylene, 0% to 20% polypropylene, and 40% to 70% calcium powder; The seventh, eighth, and ninth layers have the same composition and include vinyl acetate and / or methyl acrylate.

10. A food preservation bag, characterized in that, The preservation packaging includes a preservative and a packaging bag. The packaging bag is made of the packaging material described in any one of claims 1 to 9. The packaging bag includes a heat-sealing layer and a main body layer stacked from the inside to the outside along the thickness direction. The heat-sealing layer is disposed on the inner side, and the main body layer is disposed on the outer side. There is a receiving cavity between the heat-sealing layers, and the preservative is disposed in the receiving cavity.

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